A major goal of the proposed project is to elucidate the role of lens electrolytes, particularly the cations calcium and magnesium, in cataract development. Studies of causes and consequences of alterations in the ionic composition of the lens will focus on both the aging and cataractous lens since human cataract is chiefly an age related disease. It remains particularly important therefore to continue investigations which identify and characterize those biochemical alterations common to cataractous and mature noncataractous lenses. The influence of ions on physiologic processes susceptible to modification or known to undergo alterations in cataract will be investigated in normal cultured lenses as well as in the cell free system to thoroughly investigate the synergistic effects of the ions on each process. If the content of lens calcium and GSH are altered, for example, the potentially cytotoxic effects of calcium on GSH synthesis will be determined under conditions in which ion levels are carefully controlled and selectively altered. The direct contribution of ionic alterations to opacification will be assessed by monitoring lens opacities of experimental cataracts using a laser scanning system. Parameters such as degree or location of opacity can be correlated with changes in biochemical properties such as ion, substrate, or GSH levels to determine whether calcium elevation, for instance, is a unique or sufficient requirement for opacification or whether additional alterations are required. Experiments are also necessary to determine the effect of altering the ionic environment of lens proteins on the conformation of the crystallins since high molecular weight aggregates are potential light scattering centers. The process of aggregation in opaque regions of the intact lens as well as modification of tertiary protein structure prior to aggregation will be investigated using HPLC and difference absorption spectroscopy techniques.